JP2021019196A - Separator for electric double layer capacitor and manufacturing method thereof - Google Patents

Abstract

To provide a separator for an electric double layer capacitor that has electrical insulation, prevents short circuit between positive and negative electrodes, and can achieve both contradictory characteristics of excellent wettability by electrolyte and excellent electrolyte retention performance.SOLUTION: A laminate of melt-blow non-woven fabric thin films is made of a non-woven fabric manufactured by a melt-blow method using a heat-resistant resin as a raw material, and at least two layers of melt-blow non-woven thin films are stacked and pasted. Since pore diameter distribution is set in a specific range, a separator for an electric double layer capacitor made of the melt-blown non-woven thin film laminate having high high-temperature stability and excellent electrolyte retention is provided. Such a melt-blown non-woven fabric thin film laminate can be produced by subjecting at least two melt-blow non-woven fabric raw fabrics to a first calendering treatment under high temperature conditions by a metal roll and a second calendering treatment under special conditions by an elastic roll.SELECTED DRAWING: None

Description

The present invention relates to a separator for an electric double layer capacitor (hereinafter, may be referred to as a "separator") and a method for manufacturing the same, and more specifically, a non-woven fabric manufactured by a melt blow method using a heat-resistant resin as a raw material (hereinafter, referred to as "separator"). , "Melt-blow non-woven fabric".) The present invention relates to a separator for an electric double layer capacitor and a method for manufacturing the same, which is composed of a thin melt-blow non-woven fabric laminate formed by laminating a plurality of sheets to form a thin film.

In recent years, with the miniaturization and diversification of electronic devices, thin and high-performance power storage devices have been demanded. In particular, with the expansion of applications to electric vehicles and the like, it is required to increase the capacity and the life of the electric double layer capacitor, and the development of an improved electric double layer capacitor capable of rapid charging and discharging is eagerly desired.
Such an electric double layer capacitor has a basic structure including an electrode pair composed of a positive electrode and a negative electrode, a separator arranged between the two electrodes, and an electrolytic solution impregnating the separator, and the performance of the separator is an electric double layer. Since it greatly affects the performance of capacitors, many proposals have been made for separators. For example, Patent Document 1 discloses a separator for an electric double layer capacitor including a fiber layer including ultrafine fibers having a fiber diameter of 4 μm or less and thick fibers having a fiber diameter of 7 μm or more. According to the separator, even if a high pressure is applied, the presence of the thick fibers can prevent the separator from breaking, secure a certain amount of voids, and contain ultrafine fibers. There is a description that the retention of the ionic solution can be ensured.
Further, Patent Document 2 discloses a separator for an electric double layer capacitor composed of a non-woven fabric having a two-layer structure of a glass fiber-containing layer and a cellulose fiber layer.

However, according to the prior art as described above, the control of the dispersed state of fibers and pores in the three-dimensional space in the thickness direction of the separator has not yet been sufficiently disclosed, and the conventional separator for an electric double layer capacitor has not been sufficiently disclosed. Cellulose-based fibers and glass fibers are used as the above, but it is not possible to effectively control the pore distribution in the three-dimensional space only by using the ultrafine fibers of such fibers, and as a result, the electrolyte liquid retention property. It has been pointed out that the problem is low and the internal resistance is high. Further, these materials have a drawback that the mechanical strength is weak.

Further, a separator in which non-woven fabrics having different manufacturing methods are laminated, such as SMS (spun bond / melt blow / spun bond), has been proposed, but the bulky non-woven fabric is thinned and calendared at a high temperature in order to improve the interlayer adhesion. Even if the pore distribution on the surface can be controlled to some extent, an excessively crushed portion is generated, and a three-dimensional structure effective as a separator cannot be realized. Therefore, there is a problem that a separator having low air permeability and high internal resistance is formed. Further, such a non-woven fabric laminate has a problem that the shrinkage rate is large at a high temperature because the non-woven fabrics having different manufacturing methods are simultaneously pressure-bonded. Further, due to the nature of the non-woven fabric, shades are generated in the arrangement structure of the constituent fibers, and the physical properties of the base material become non-uniform. Therefore, it has been required to reduce the shades.

Japanese Unexamined Patent Publication No. 2003-45752 JP-A-2017-168743

Therefore, the subject of the present invention is to have the contradictory characteristics of having electrical insulation, being able to prevent a short circuit between the positive electrode and the negative electrode, and at the same time being excellent in wettability by the electrolytic solution and liquid retention property of the electrolytic solution. To provide a separator for an electric double layer capacitor and a method for producing the same, which can be compatible with each other, reduce the shading generated in the arrangement structure of the constituent fibers, and are composed of a melt-blown non-woven fabric laminate having uniform characteristics. is there.

Therefore, as a result of diligent studies in order to solve the above-mentioned problems of the present invention, the present inventor disperses fibers and pores on the surface of a separator composed of a melt-blown non-woven fabric laminate and in a three-dimensional space in the thickness direction. Focusing on the fact that the above-mentioned problems of the present invention can be solved if the state, that is, fibers and pores of an appropriate size can be arranged in a well-balanced manner, the completion of the present invention has been reached based on such findings.
That is, in view of solving the problem, as described above, from at least two layers of the melt-blown non-woven fabric thin film manufactured by using a heat-resistant resin as a raw material resin in order to realize a well-balanced arrangement of fibers and pores of an appropriate size. The grain size is adjusted to 50 g / m2 or less, the thickness is 50 μm or less, the average fiber diameter is controlled to 0.5 to 15 μm, and the pore size distribution is set to the following specific range. By doing so, the above-mentioned contradictory characteristics can be compatible with each other. A melt-blown non-woven thin film laminate capable of achieving both of these characteristics can be obtained by a two-step calendering process of a first calendering process using a metal roll under high temperature conditions and a second calendering process provided with an elastic roll. I found that I could do it. In particular, by using a non-woven fabric thin film laminate produced by the melt blow method using only a non-woven fabric, a stable pore size distribution can be maintained and the above-mentioned characteristics can be stabilized, so that the yield is also high in the production process. Some of them are good, can be produced at low cost, and have extremely high industrial utility value.

Thus, the gist of the present invention is as shown in the following (1) to (14).
In the present specification, the inventions according to (1) to (6) are the first invention, the inventions according to (7) to (13) are the second invention, and the invention according to (14) is the third invention. There is that.

(1) A separator for an electric double layer capacitor composed of a melt-blow non-woven fabric thin film laminate in which at least two layers of melt-blow non-woven fabric thin films are laminated.
The average fiber diameter of the fibers constituting the melt-blown non-woven thin film laminate is 0.5 to 15 μm, the Garley air permeability is 1 to 40 s / φ10 / 300 cc, and the heat shrinkage is 150 ° C. for 1 hour. After the heat treatment under the conditions, the shrinkage change of either the shape in the MD direction or the CD direction is expressed by the dimensional change rate, which is 1.2% or less, and the electrolyte liquid retention rate is 260% or more. Separator for electric double layer capacitors.

(2) The electric double layer capacitor according to (1) above, wherein the average fiber diameters of the constituent fibers of each layer of at least two layers of the melt-blown non-woven fabric thin film constituting the melt-blown non-woven fabric thin film laminate are substantially the same or different from each other. Separator for.

(3) The melt-blown non-woven fabric thin film laminate is an interlayer adhesion processed body formed by partial heat fusion of fibers existing at the interface between layers of at least two layers of the melt-blow non-woven fabric thin film constituting the same (3). The separator for an electric double layer capacitor according to 1).

(4) The separator for an electric double layer capacitor according to (1) above, wherein 50% or more of the total pores of the melt-blown non-woven fabric thin film laminate occupy a pore diameter in the range of 3 to 7 μm.

(5) The separator for an electric double layer capacitor according to (1) above, wherein the melt-blown non-woven fabric thin film laminate has a pore size distribution satisfying the following 1 to 5.
1. 1. Maximum pore diameter: 15 μm or less 2. Minimum pore diameter: 3 μm or less 3. Average pore diameter: 8 μm or less 4. Maximum pore diameter / average pore diameter: less than 2.00 5. Maximum pore diameter / minimum pore diameter: 5.00 or more

(6) The separator for an electric double layer capacitor according to (1) above, wherein the constituent material of the melt-blown non-woven fabric thin film laminate is a heat-resistant resin.

(7) A method for manufacturing a separator for an electric double layer capacitor, which is composed of a melt-blow non-woven fabric thin film laminate in which at least two layers of melt-blow non-woven fabric thin films are laminated.
(A) At least two melt-blown non-woven fabric raw materials are superposed, and the calendar mechanism having a metal roll suppresses the processing temperature conditions above the glass transition point of the raw material resin and the crushing of the constituent fibers of the melt-blown non-woven fabric raw material. In addition, the first calendar processing step to be performed in the calendar processing under the pressure condition adjusted to the condition that the film can be thinned, and
(B) The calendar processing intermediate obtained by the first calendar processing step has an effective processing temperature condition and the crushing of the constituent fibers of the non-woven fabric is suppressed by the calendar mechanism having at least one elastic roll. The melt blow is characterized by having a calendar processing step including at least a second calendar processing step to be subjected to calendar processing under pressurized conditions adjusted to a condition capable of thinning. A method for manufacturing a separator for an electric double-layer capacitor composed of a non-woven thin film laminate.

(8) The method for manufacturing an electric double layer capacitor separator according to (6) above, wherein in the first calender processing step, the processing temperature condition above the glass transition point is 130 ° C. or higher.

(9) In the first calendering process, the linear pressure of the metal roll is 200 N / mm or less among the pressure conditions adjusted so as to suppress the crushing of the constituent fibers of the melt-blown nonwoven fabric. The method for manufacturing a separator for an electric double layer capacitor according to (7).

(10) In the second calendar processing step, the calendar mechanism includes at least a combination of a pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and a metal roll. The method for manufacturing a separator for an electric double layer capacitor according to 7).

(11) In the second calendar processing step, the calendar mechanism includes at least a combination of a pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and an elastic roll. The method for manufacturing a separator for an electric double layer capacitor according to 7).

(12) The method for producing an electric double layer capacitor separator according to (7) above, wherein the effective processing temperature condition is 130 ° C. or lower in the second calender processing step.

(13) The method for producing an electric double layer capacitor separator according to (7) or (12) above, wherein in the second calendering process, the elastic material of the elastic roll is a synthetic resin.

(14) Next step:
Next step:
(A) At least two melt-blown non-woven fabric raw materials are superposed, and the metal roll suppresses the processing temperature conditions above the glass transition point of the raw material resin and the crushing of the constituent fibers of the melt-blown non-woven fabric raw material, and makes the material thinner. The first calendering process, which is subjected to calendering under pressurized conditions adjusted to the possible conditions,
(B) The calendar processing intermediate obtained by the first calendar processing step has an effective processing temperature condition and the crushing of the constituent fibers of the non-woven fabric is suppressed by the calendar mechanism having at least one elastic roll. A separator for an electric double layer capacitor manufactured by a method including a second calendar processing step of being subjected to calendar processing under pressurized conditions adjusted to a condition capable of thinning.

The present invention has the above-described configuration, and according to the first invention, the separator for an electric double layer capacitor composed of a melt-blown non-woven fabric thin film laminate has a specific pore size distribution. Despite its small thickness, significant deformation of the constituent fibers of the non-woven fabric is suppressed, and there is no formation of transparent spots due to film formation of the entangled parts, and the Garley air permeability is in a good range, and heat at high temperatures. It has the effect of having a small shrinkage rate.
Further, by laminating and combining non-woven fabric layers having fibers having the same or different average fiber diameters, a specific pore size distribution can be obtained, and in particular, the liquid absorption property and the liquid retention property of the electrolytic solution can be improved. By using a melt-blown non-woven thin film laminate having such characteristics as a separator, it has been successfully applied to an electric double layer capacitor (EDLC), thereby realizing stable performance of the electric double layer capacitor and ensuring safety. It can be secured and its productivity can be improved.
According to the second invention, a calendering process is provided by combining two steps of the first calendering process and the second calendering process, and in particular, at least two melt-blown non-woven fabric raw fabrics are superposed to each other. As shown in Examples and Comparative Examples described later, the melt-blown non-woven fabric thin film laminate having the above-mentioned performance obtained by the first invention and the second invention is composed for the first time by being subjected to the calender processing step of the above. It is possible to exert a remarkably remarkable effect such as being able to provide a separator for an electric double layer capacitor.
Further, according to the third invention, the same effect as that of the first invention and the second invention can be obtained.

It is a graph which shows the pore diameter distribution of the PBT melt blow non-woven fabric thin film two-layer laminated body produced by Example 1. It is a graph which shows the pore diameter distribution of the PBT melt blow non-woven fabric thin film three-layer laminated body produced by Example 2. It is a graph which shows the pore diameter distribution of the PBT non-woven fabric thin film single layer body a (single layer comparative product (a)) produced by the method of Comparative Example 1. It is a graph which shows the pore diameter distribution of the PBT non-woven fabric thin film single layer d (single layer comparative product (d)) produced by the method of Comparative Example 4. It is a graph which shows the pore diameter distribution of the PP non-woven fabric thin film monolayer e (single-layer comparative product (e)) produced by the method of Comparative Example 5. It is a graph which shows the pressure-permeation flow rate curve for obtaining the average pore diameter, the maximum pore diameter and the minimum pore diameter by a bubble point method.

Hereinafter, the present invention will be described in detail.
A. First invention 1. Separator for electric double layer capacitor composed of melt blow non-woven thin film laminate:
According to the first invention, there is provided a separator for an electric double layer capacitor composed of a melt-blown non-woven fabric thin film laminate made of a heat-resistant resin. Such a melt-blown non-woven fabric thin film laminate has at least the following physical property values.
That is,
-Thickness is 50 μm or less
・ The basis weight is 5 to 100 g / m2.
-The average fiber diameter is 0.5 to 15 μm,
・ Garley air permeability is 1-40s / φ10 / 300cc.
-The heat shrinkage rate is 1.2% or less in terms of the dimensional change rate, respectively, for the shrinkage change of the shape in either the MD direction or the CD direction even after the heat treatment under the heating condition of 150 ° C. for 1 hour. ..
Further, as described above, although the thickness is reduced to 50 μm or less, the electrolytic solution absorbing performance and the electrolytic solution retaining performance are excellent. Specifically, in Examples and Table 1 described later. As shown, it is also possible to realize an electrolytic solution absorption rate of 15 seconds or less and an electrolytic solution retention rate of 280% or more.
Further, the openness of the melt-blown nonwoven fabric thin film constituting the electric double layer capacitor according to the present invention was sufficiently maintained by the presence of pores existing in the gaps between the fibers constituting the melt-blown nonwoven fabric thin film laminate observed by SEM. It is a thing.

2. 2. Structure of Melt Blown Nonwoven Thin Film Laminate:
(1) Characteristics The melt-blown non-woven fabric thin film laminate according to the present invention is a non-woven fabric laminated body obtained by laminating and laminating at least two non-woven fabric layers. In particular, it is preferable to adopt a non-woven fabric laminated body in which at least two or more non-woven fabric layers are laminated and laminated, depending on the application, because it has the following characteristics as compared with a single layer. The melt-blown non-woven fabric thin film laminate includes (A) a non-woven fabric layer having the same physical characteristics and (B) a non-woven fabric layer having fibers having at least different average fiber diameters among the physical properties. You can list things.

As described later, in the above-mentioned "laminated non-woven fabric processed body", the non-woven fabric layers are formed by pressure bonding with each other by, for example, a first calendering process under high temperature conditions and a second calendering process under special conditions. It includes the processed product obtained by. By pressure-bonding formation, an interlayer adhesion processed body is formed in which some of the fibers constituting the non-woven fabric layer are bonded to each other by heat fusion. The heat-sealed portion may occupy 50% or less of the fibers existing at each interface of the non-woven fabric layer, and can be appropriately selected from the viewpoint of maintaining the formation of the non-woven fabric thin film laminate.
(A) The non-woven fabric laminated body formed by laminating the non-woven fabric layers having the same physical characteristics is a case where the average fiber diameter values of the constituent fibers of the non-woven fabric layers of at least two layers are substantially the same, and other physical characteristics. The values, for example, at least two or more physical property values such as texture, tensile strength, and tensile elongation may be substantially the same. According to this configuration, for example, when the average fiber diameter is the same, the variation in physical properties is made uniform as compared with a single layer, especially by laminating a laminate of fine fibers, and the separator for an electric double layer capacitor can be used. When used, it is possible to prevent a short circuit, improve the tensile strength, and improve the electrolyte liquid retention property.

On the other hand, according to (B) bonding of a non-woven fabric layer composed of at least two layers having fibers having different average fiber diameters, the obtained melt-blown non-woven fabric thin film laminate has tensile strength and garley air permeability as shown in Examples. The degree can be improved, and the liquid absorption performance and the liquid retention performance of the electrolytic solution can also be improved. In particular, a laminated non-woven fabric formed by laminating obtained by combining non-woven fabric layers having fine fibers and thick fibers can improve tensile strength, Garley air permeability, electrolyte liquid absorption performance and liquid retention performance.

The fine fibers are specifically those having an average fiber diameter of 0.5 to 10 μm, preferably 1 to 5 μm, and more preferably 1.5 to 4 μm, while the thick fibers are specifically. Is an average fiber diameter of 1 to 15 μm, preferably 1.5 to 10 μm, more preferably 2 to 5 μm, and is a non-woven fabric layer having fine fibers and thick fibers in which these average fiber diameters do not overlap with each other. The combination is preferred.

(2) Pore Structure of Melt Blow Nonwoven Fabric Thin Film Laminate The melt blow nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention includes fibers arranged in a three-dimensional space in the surface and thickness directions. Due to the arrangement of the fiber groups, the fibers are formed from the pores formed in the gaps thereof. Since the material of the melt-blown non-woven thin film laminate is a synthetic resin, it has electrical insulation properties, and due to its pore structure, it has both electrolyte liquid retention properties and contradictory properties. It has uniform physical properties and has at least the following two controlled pore size distributions as described below.

A. The first point is that the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention has 50% or more of the pores having a pore diameter in the range of 3 to 7 μm. is there.
The proportion of pores in the range of 3 to 7 μm in pore diameter is preferably 60% or more, more preferably 70% or more, and the uniformity of pore diameter is extremely high.
FIGS. 1 and 2 below show the pore size distributions of the two-layer and three-layer products of the PBT melt-blown non-woven thin film laminate according to Examples 1 and 2, respectively. According to this, the size of the pore diameter is extremely controlled, and as a result, the formation of uneven appearance is controlled, the air permeability is maintained, and the electrolyte liquid retention property is excellent.
On the other hand, when the pore diameter is in the range of 3 to 7 μm or less, the variation in characteristics is reduced, but the air permeability is lowered, whereas in the pore diameter range of 3 to 7 μm or more, the air permeability is improved. However, the variation in characteristics becomes large, and there arises a problem that the appearance and other physical properties become unstable.
Further, FIGS. 3, 4 and 5 show the pore size distributions of the nonwoven fabric monolayers produced by Comparative Example 1, Comparative Example 4 and Comparative Example 5, respectively, as shown in FIG. The pore diameters of the PBT melt-blown non-woven fabric monolayers according to Comparative Example 1 showed wide variations, and it was shown that the uniformity of the pore diameters was significantly lower than that of the melt-blown non-woven fabric laminates of Examples 1 and 2.
Further, according to FIG. 4, the pore size distribution of the melt-blown nonwoven fabric monolayer according to Comparative Example 4 also has a peak range of 3 to 7 μm of the melt-blown nonwoven fabric thin film laminate according to the present invention, as shown in FIGS. 1 and 2. It deviates.

I. The second point is that the melt-blown non-woven thin film laminate constituting the separator for the electric double layer capacitor according to the present invention has the following pore size distributions (1) to (5):
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter / average pore diameter: less than 2.00 (5) Maximum pore diameter / minimum Pore diameter: The point is that 5.00 or more is satisfied, and in particular, the point that the "maximum pore diameter / average pore diameter" in (4) is less than 2.00, and the "maximum pore diameter" in (5). There is specificity in that "/ minimum pore diameter" is 5.00 or more.

The maximum pore diameter of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is preferably 15 μm or less. When the maximum pore diameter is 15 μm or less, the uniformity of the pore diameter becomes excellent, electrical insulation can be ensured, and the possibility of a short circuit can be controlled. Further, the electrolyte liquid retention property can be improved, and from that viewpoint, it is more preferably 13 μm or less, and particularly preferably 11 μm or less.

The minimum pore diameter of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is preferably 3 μm or less. When the minimum pore diameter is 3 μm or less, the electrolyte liquid retention property can be maintained and the possibility of a short circuit can be reduced. The lower limit of the minimum pore diameter is not particularly limited, but is 1 μm or more, preferably 1.5 μm or more from the viewpoint of electrolyte liquid retention.

The average pore diameter of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is preferably 8 μm or less. When the average pore diameter is 8 μm or less, the possibility of short circuit is reduced. Further, when it is 8 μm or less, the electrolyte liquid retention property is also excellent.

The ratio of the maximum pore diameter to the average pore diameter (maximum pore diameter / average pore diameter) of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is less than 2.00, preferably 1. .50 or more. When the maximum pore diameter / average pore diameter is less than 2.00 and is 1.50 or more, the pore diameter distribution becomes uniform in a specific pore diameter range, and the electrolyte liquid retention property is unexpectedly significantly improved. Was found from the results of numerous experiments. From the viewpoint of electrolyte liquid retention, it is preferably 1.90 or less, more preferably 1.85 or less, particularly preferably 1.75 or less, and the range is 1.50 or more.
The ratio of the maximum pore diameter to the minimum pore diameter (maximum pore diameter / minimum pore diameter) of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 5.00 or more. When the maximum pore diameter / minimum pore diameter is 5.00 or more, the pore diameter distribution becomes uniform within a specific pore diameter range, and the electrolyte liquid retention property is unexpectedly significantly improved. From the viewpoint of electrolyte liquid retention, it is preferably 5.30 or more, more preferably 5.50 or more, and particularly preferably 5.70 or more. On the other hand, the upper limit value is 7.00, preferably 6.00 or less.

3. 3. Constituent Material of Melt Blow Nonwoven Fabric Thin Film Laminate The constituent material of the melt blow non-woven fabric thin film laminate according to the present invention is a component containing a heat-resistant resin and may be a mixture of two or more types of heat-resistant resin. Derived from the anti-component. Specific examples are as follows.

As the raw material resin for the melt-blown nonwoven fabric according to the present invention, a heat-resistant resin is selected from the viewpoint of maintaining high-temperature stability.
As the heat-resistant resin, a thermoplastic synthetic resin having a melting point of 200 ° C. or higher is preferable, and specific examples thereof include polyester, polyamide, polyimide, polyacrylonitrile, polyarylene sulfide, polycarbonate, polyphthalamide, and polyolefin. it can.

Examples of the polyester include polyethylene terephthalate, polybutylene terephthalate (hereinafter, may be abbreviated as PBT), polybutylene isophthalate, polybutylene adipate, poly (1,6-hexamethylene terephthalate, poly (ethylene-2,6-). (Naphthalate), poly (1,4-cyclohexylene methylene terephthalate) and the like. These may be homopolymers, copolymers, or mixtures thereof. Among these polyesters, polybutylene in particular. Terephthalate, a mixture of polybutylene terephthalate and polybutylene isophthalate, etc. is preferable as the raw material resin for the melt-blow non-woven thin film laminate according to the present invention. By using these, the melt-blow spinnability is improved and the tensile strength of the melt-blow non-woven thin-film laminate The number average molecular weight of polybutylene terephthalate is preferably 5,000 to 20,000, and an IV value of 0.6 to 0.9 is preferable.

Examples of the polyamide (hereinafter, may be abbreviated as PA) include nylon 6, nylon 66, nylon 6-66 copolymer, nylon 12, nylon 6-12 copolymer, nylon 46 and the like. As the melt blown nonwoven fabric, one having a molecular weight as low as possible is preferable because it has good spinnability and fine fibers can be obtained. For example, PA having a number average molecular weight of 10,000 to 25,000 is preferable.

Examples of the polyarylene sulfide include polymers having excellent heat resistance and chemical resistance, in which 90 mol% or more of the constituent units are composed of [C6H4S], and in particular, the melt viscosity (V6) is 200 to 200 to. 500-poise polyphenylene sulfide (hereinafter, may be abbreviated as PPS) is preferable.

The polyphthalamide is not particularly limited, but contains a terephthalamide unit, an isophthalamide unit, and the like, and is, for example, a hexamethylene terephthalamide-isophthalamide-adipoamide terpolymer (molar ratio 65:). 25:10) and the like can be exemplified. Examples of the raw material resin for the melt-blown non-woven fabric thin film laminate include those having a melt viscosity of 100 to 1000 Pas.
Examples of the polyolefin include polymethylpentene and cyclic olefin polymers.

4. Physical Properties of Melt Blow Nonwoven Fabric Thin Film Laminated Body Next, the physical property values that the melt blow nonwoven fabric thin film laminate constituting the separator for the electric double layer capacitor according to the present invention should have will be described.
When the melt-blown non-woven fabric thin film laminate is composed of two or more layers of non-woven fabric thin films having different physical property values, the physical property values are the average values of all the non-woven fabric thin film layers.

(1) Average Fiber Diameter The average fiber diameter of the fibers of each non-woven fabric layer of the melt-blown non-woven fabric thin film laminate constituting the separator for the electric double layer capacitor according to the present invention is 0.5 to 15 μm, preferably 1.0 to 10 μm. More preferably, it is 1.5 to 8 μm. If the average fiber diameter is less than 0.5 μm, not only the tensile strength is weakened, but also the internal resistance of the electric double layer capacitor becomes too large as a separator. On the other hand, if the average fiber diameter exceeds 15 μm, the risk of internal short circuit may increase as a separator.

(2) Metsuke The basis weight of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 5 to 100 g / m2, preferably 7 to 50 g / m2, and more preferably 10 to 40 g / m2. .. If the basis weight is less than 5 g / m2, the tensile strength is insufficient, so that the reliability in the battery assembly is lowered, and the separator is not preferable because shorts are likely to occur. On the other hand, if the basis weight exceeds 100 g / m2, the internal resistance of the separator may increase.

(3) Thickness The thickness of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 50 μm or less, preferably 1 to 45 μm for a separator for an electric double layer capacitor and a separator for a lithium secondary battery. , Particularly preferably 5 to 40 μm, and even more preferably 10 to 35 μm. If the thickness exceeds 1 μm, the risk of an internal short circuit is suppressed as a separator, while if it exceeds 50 μm, the battery capacity may decrease.

(4) Garley Air Permeability The Garley air permeability of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 1 to 40 s / φ10 / 300 cc, preferably 5 to 30 s / φ10 / 300 cc. is there. If the Garley air permeability is less than 1 s / φ10 / 300 cc, the risk of internal short circuit as a separator increases, while if it exceeds 40 s / φ10 / 300 cc, the internal resistance of the separator increases.
As will be described later, "Garley air permeability" is measured by a measurement method based on JIS P8117 (2009) "Paper and paperboard-Air permeability and air permeability resistance test method" (intermediate region) -Gurley method. It means the result obtained.

(5) Tensile Strength The tensile strength of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 2 to 50 N / 25 mm width, preferably 5 to 40 N / 25 mm width. If the tensile strength is less than 2N / 25mm width, it is likely to break during battery assembly. On the other hand, if the tensile strength exceeds 50 N / 25 mm width, the elongation is extremely lowered, and there is a possibility that a defect is likely to occur due to a decrease in the degree of freedom during assembly.

(6) Tensile Elongation The tensile elongation of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is 1 to 100%, preferably 5 to 80%. If the tensile elongation is less than 1%, it is likely to break during assembly. On the other hand, if the tensile elongation is 100% or more, necking is likely to occur, and stable assembly may be difficult.

(7) Heat Shrinkage Rate The heat shrinkage rate of the melt-blown nonwoven fabric thin film laminate constituting the separator for an electric double layer capacitor according to the present invention at 120 ° C. for 1 hour is 1.0% or less. It is preferably 0.5% or less, 1.2% or less, preferably 1.0% or less under a heating environment at 150 ° C. for 1 hour. It is desirable that this value satisfies at least one of the MD direction and the CD direction, more preferably both. If the heat shrinkage rate is high, the separator at the end may shrink due to the internal temperature rise due to the occurrence of an abnormality in the electric double layer capacitor in a high temperature environment, and problems such as internal short circuit may occur due to contact between the positive and negative electrodes. ..

(8) Electrolyte Liquid Absorption Rate The electrolyte liquid absorption property of the melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention is such that an electrolytic solution, for example, propylene carbonate, can be smoothly used as the separator due to the pore structure. According to the present invention, it is possible to provide a material having an electrolytic solution absorption rate of 20 seconds or less, and further 10 seconds or less, as required by the measurement method described later. ..
(9) Electrolyte Liquid Retention Rate The melt-blown non-woven thin film laminate constituting the separator for electric double layer capacitors according to the present invention is used as a separator after absorbing the electrolytic solution due to the dispersed state of the constituent fibers and the peculiarity of the pore structure. It is excellent in liquid retention property, shows 260% or more by the measurement method described later, and can provide 360% or more, and further about 380%.
(10) Static electricity The amount of static electricity in the melt-blown non-woven thin film laminate constituting the electric double layer capacitor according to the present invention is small as shown in Table 1, and the sticking of the production line is reduced, which contributes to the improvement of battery productivity. be able to.
As described above, the melt-blown nonwoven fabric laminate constituting the separator for an electric double layer capacitor according to the first invention is a laminate in which at least two or more layers of melt-blown nonwoven fabric made of heat-resistant resin are laminated.
Of all the pores, the proportion of pores occupying the pore diameter range of 3 to 7 μm is 50% or more, preferably 60% or more.
And the following (1) to (5):
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter / average pore diameter: less than 2.00 (5) Maximum pore diameter / minimum Pore diameter: It has a pore size distribution that satisfies 5.00 or more, and has a pore size distribution.
At least the following physical characteristics;
・ Thickness is 50 μm or less,
・ Metsuke is 5 to 100 g / m2,
・ Average fiber diameter is 0.5 to 15 μm,
・ Garley air permeability is 1-40s / φ10 / 300cc,
-The heat shrinkage is 1.2% or less, respectively, in terms of the shrinkage change of the shape in either the MD direction or the CD direction even after the heat treatment under the heating condition of 150 ° C. for 1 hour. ..
As one method, such a melt-blown non-woven fabric thin film laminate can be produced through the following calendar processing step.
That is, (a) the laminate obtained by laminating the melt-blown non-woven fabric raw fabric is subjected to a processing temperature condition equal to or higher than the glass transition point of the heat-resistant resin and crushing of the constituent fibers of the melt-blown non-woven fabric raw fabric is suppressed by the metal roll. The first calendering process to be subjected to calendering under pressurized conditions adjusted so as to
(B) The calendering processing intermediate obtained in the first calendering processing step is subjected to an effective processing temperature condition and a pressurizing condition adjusted so as to suppress the crushing of the constituent fibers of the nonwoven fabric by an elastic roll. A melt-blown nonwoven fabric laminate having at least the above-mentioned physical characteristics can be obtained by the calendering process including the second calendering process step to be subjected to the calendering process below.

B. Second Invention According to the second invention, there is provided a method for manufacturing a separator for an electric double layer capacitor composed of a melt-blown non-woven thin film laminate.
That is, it is a method for manufacturing a separator for an electric double layer capacitor, which is composed of a melt-blow non-woven fabric thin film laminate formed by laminating and thinning a melt-blow non-woven fabric raw fabric produced using a heat-resistant resin as a raw material resin.
Provided is a method for producing a melt-blow non-woven fabric laminate, which comprises laminating the melt-blow non-woven fabric and subjecting it to at least (a) a first calender processing step and (b) a second calender processing step.
Here, the “melt-blown non-woven fabric raw fabric” means a non-woven fabric manufactured by the melt-blow method and is a target non-woven fabric to be thinned into a non-woven fabric thin film laminate.

1. 1. Melt-blow non-woven fabric raw fabric The physical properties of the melt-blow non-woven fabric used as the base material for manufacturing the melt-blow non-woven fabric laminate constituting the separator for the electric double layer capacitor according to the present invention, and the method for manufacturing the melt-blow non-woven fabric raw fabric having such physical properties are as follows. Explain to.
The melt-blown non-woven fabric raw material constituting the separator for an electric double layer capacitor according to the present invention is manufactured by a melt-blow method using a heat-resistant resin as a raw material resin.
The heat-resistant resin is as described above, and can be appropriately selected from such heat-resistant resins and used. However, polybutylene terephthalate is suitable for the purpose of the present invention as described above, and melt blow described below. The manufacturing conditions for the non-woven fabric raw fabric are based on the case where polybutylene terephthalate is used as the heat-resistant resin.

The melt-blow non-woven fabric raw fabric is an important element for the production of the melt-blow non-woven thin film laminate according to the present invention, and preferably has at least the following physical properties.
(1) Metsuke The basis weight of the melt-blown nonwoven fabric according to the present invention is 4 to 80 g / m2, preferably 5 to 50 g / m2, and more preferably 6 to 40 g / m2. If the grain size does not reach 4 g / m2, the tensile strength of the melt-blown non-woven fabric thin film laminate obtained after the calendering process is insufficient. On the other hand, if the grain size exceeds 80 g / m2, fluffing increases and the non-woven fabric thin film layer is stably laminated. Problems such as difficulty in manufacturing the body may occur.
(2) Thickness The thickness of the melt-blown nonwoven fabric according to the present invention varies depending on the type of raw material resin, production conditions, etc., but is 50 to 800 μm, preferably 60 to 400 μm, and more preferably 70 to 300 μm. As the separator for an electric double layer capacitor according to the present invention, a melt-blown non-woven fabric raw material adjusted to a thickness of 300 μm or less, particularly preferably 250 μm or less is preferable.
(3) Air permeability The air permeability of the melt-blown nonwoven fabric according to the present invention is 10 to 400 cc / cm2 / s, preferably 20 to 300 cc / cm2 / s. When the air permeability is less than 10 cc / cm2 / s, the galley air permeability of the melt-blown non-woven thin film laminate obtained after the first calender processing becomes high, exceeding 40 s / φ10 / 300 cc, while the air permeability is 400 cc / s. If it exceeds cm2 / s, the calender air permeability of the melt-blown non-woven fabric thin film laminate decreases, and becomes less than 1 s / φ10 / 300 cc. As described above, the melt-blow non-woven fabric thin film laminate having a specific range of galley air permeability is obtained. There is a problem that the risk of being unable to manufacture increases.
(4) Tensile strength The tensile strength of the melt-blown non-woven fabric raw fabric according to the present invention is at least 1 N / 25 mm width or more so as to provide a melt-blown non-woven fabric thin film laminate having a tensile strength of 2 to 50 N / 25 mm width. Preferably, the width is 3N / 25 mm or more. If the tensile strength of the melt-blown non-woven fabric raw fabric does not reach 1 N / 25 mm width, there arises a problem that a melt-blown non-woven fabric thin film laminate having sufficient tensile strength cannot be obtained.
(5) Tensile Elongation The tensile elongation of the melt-blown nonwoven fabric according to the present invention is 1 to 150%, preferably 10 to 100%.
(6) Average Fiber Diameter The average fiber diameter of the fibers constituting the melt-blown nonwoven fabric according to the present invention is 0.5 to 15 μm, preferably 1 to 10 μm, and more preferably 1.3 to 5 μm. is there.

2. 2. Melt-blow method The melt-blow method for producing the melt-blow non-woven fabric raw fabric according to the present invention is not particularly limited, and is, for example, the method described in US Pat. No. 3,650866 and US Pat. No. 3,978185 (ExxonMobil). Is preferable, and the melt blow method described below can be adopted as a method similar to these.
As a melt blow method, molten raw material resin is discharged as a molten polymer from a plurality of nozzle holes arranged in a row, and high-temperature and high-speed air is injected from an injection gas port installed adjacent to an orifice die to melt the melt. A method is adopted in which the polymer is fibrillated and the fiber flow is collected. Specifically, the following method is adopted.

The raw material resin is melted at an extruder temperature of 210 to 380 ° C., then fed to a die set at 250 to 380 ° C. and discharged from a die nozzle, and at the same time, stretched by a high temperature air blow gas of 260 to 380 ° C. to form fine fibers. , Collect in a collector installed at a position away from the nozzle.

In the melt blow device die, the nozzle hole diameter is preferably 0.1 to 1 mmφ, more preferably 0.2 to 0.8 mmφ. The number of nozzles is preferably 5 to 20 / cm, more preferably 10 to 15 / cm. If the nozzle hole diameter is less than 0.1 mmφ, the discharge resin pressure becomes high, while if the nozzle hole diameter exceeds 1 mmφ, the fibers cannot be thinned. Further, when the number of nozzles is less than 5 / cm, the discharge pressure of the raw material resin becomes high, while when the number of nozzles exceeds 20 / cm, the fibers are excessively fused to each other and the uniformity of the non-woven fabric is lost. It becomes.

Further, as the production conditions of the melt blow method, in the production of a melt blow nonwoven fabric using a heat-resistant resin, for example, polybutylene terephthalate resin as a raw material, the extrusion temperature is 210 to 350 ° C, preferably 230 to 330 ° C, and the die. The temperature is 250 to 350 ° C., preferably 280 to 330 ° C., and the high-speed air temperature is 260 ° C. to 380 ° C., preferably 300 to 350 ° C. If the extruder / die and air temperature are below the above range, the discharge resin pressure becomes high and fine fibers cannot be obtained. On the other hand, if it exceeds the above range, gelation of the resin is promoted and the resin deteriorates. In addition to damaging the conveyor net, the resulting non-woven fabric has poor peelability from the conveyor net, making stable production difficult. The resin discharge amount is 0.05 to 3 g / min / hole, preferably 0.1 to 1 g / min / hole. When the resin discharge amount is small, the discharge resin pressure falls below the above range and a uniform non-woven fabric cannot be obtained. On the other hand, when the resin discharge amount exceeds the above range, the discharge resin pressure increases and fine fibers are obtained. Absent.

3. 3. Calender processing The melt-blown non-woven fabric thin film laminate according to the present invention is produced by the following two-step calender processing process. The physical characteristics of the melt-blown non-woven fabric thin film can be adjusted by selecting the processing temperature conditions, processing pressure conditions (including roll linear pressure and inter-roll clearance) and processing speed conditions of each processing process as described below. ..

(A) First non-woven fabric processing process In the first non-woven fabric processing process, a non-woven fabric mechanism consisting of a combination of at least two metal rolls is used. Specifically, a melt blow method is performed using a heat-resistant resin as a raw material. The manufactured melt-blown non-woven fabric raw material is laminated, and the pressure is adjusted so that the temperature conditions above the glass transition point of the heat-resistant resin and the crushing of the constituent fibers of the non-woven fabric raw material laminate are suppressed by the metal roll. It is calendered under the conditions. As the metal calendar roll, those usually used can be adopted, but steel and an alloy material equivalent to steel are particularly preferable. As the calendar type and roll arrangement, inverted L type, Z type, upright double type, etc. (Practical Plastic Terminology Dictionary, page 151 (published by Plastics Age Co., Ltd.)) can also be adopted.

The temperature above the glass transition point of the heat-resistant resin depends on the type of the heat-resistant resin, but for the polyester resin, a temperature of 130 ° C. or higher, preferably 140 ° C. or higher is adopted. The temperature conditions are adjusted by setting the heating temperatures of both of the two metal rolls to be combined.
The upper limit of the processing temperature in the first calender processing treatment is a temperature equal to or lower than the melting point of the heat-resistant resin, and specifically, it is preferable to adopt a temperature 30 to 100 ° C. lower than the melting point. It is presumed that the first calendering treatment alleviates the residual strain during the production of the non-woven fabric and promotes the crystallization of the raw material resin. As a result, high temperature stability is improved, and high temperature shrinkage can be improved. Quantitative measurement of crystallization is difficult and measurement is also impractical. Further, as the pressurizing condition, in addition to the roll linear pressure, the clearance provided between the rolls is also included as an element affecting the thinning. The size of the clearance is set so that the thickness of the calendering intermediate after the first calendaring treatment becomes a predetermined level, and the crushing or deformation of the fibers in the melt-blown nonwoven fabric can be suppressed. It has been adjusted. As the linear pressure of the roll, it is preferable to adopt a processing pressure of 200 N / mm or less, preferably 30 to 170 N / mm, and more preferably 50 to 150 N / mm.
Under such calendering conditions, a melt-blown non-woven fabric thin film laminate having a small shrinkage rate under high temperature conditions, a small garley air permeability, and a small internal resistance can be obtained. The clearance between the rolls can be selected within a range necessary for adhesion of at least two layers of the melt-blown non-woven fabric raw fabric layer and transmission of a temperature capable of promoting crystallization.

The processing speed condition is 1 to 50 m / min, preferably 2 to 30 m / min, and more preferably 3 to 20 m / min. If it is less than 1 m / min, the productivity is low, while if it exceeds 50 m / min, there arises a problem that heat for relaxing strain and promoting crystallization is not sufficiently transferred.

(B) Second Calender Processing Process In the second calender processing process, which is one element of the manufacturing process of the melt-blown non-woven fabric thin film laminate according to the present invention, an elastic roll is used as the calender mechanism. The combination of the pair of processing rolls can be selected from the combination of two elastic rolls of the elastic roll and the elastic roll, or the combination of the elastic roll and the metal roll. Among these combinations of processing rolls, those using a combination of a metal roll and an elastic roll are particularly preferable. As for the combination of the processing roll and the processing roll, a pair of combinations consisting of two rolls and a plurality of combinations of 4 to 6 can be used. Regarding the format of the calendar and the arrangement of the rolls, the same format as the format that can be used in the first calendar processing step can be adopted, and the arrangement of the metal rolls can be obtained by appropriately combining the metal rolls and the elastic rolls. Good. As the metal roll, the same one used in the first calendering process can be used, and steel and an alloy material equivalent to steel are preferable. As the material of the elastic roll to be combined with the metal roll, a material having a high coefficient of friction and a material made of a hard synthetic resin is preferable, and for example, synthetic rubber or the like can be used. The hardness of the roll is a shore D hardness of 60 or more, preferably 70 to 90, for the purpose of adjusting the thickness and smoothness of the melt-blown non-woven fabric thin film laminate of the present invention.

In the second calendering process, the calendering intermediate obtained in the first calendering process is sandwiched between the metal roll and the elastic roll, and the temperature is 130 ° C. or lower, preferably 120 ° C. or lower, and further. The processing is preferably carried out under a processing temperature condition of 110 ° C. or lower and a pressure condition in which the crushing of fibers in the intermediate can be controlled. In the second calender processing step, the lower limit of the processing temperature is at least the glass transition point and depends on the type of the raw material resin, but for example, a temperature of 60 ° C. or higher is preferable, and more preferably 80 ° C. or higher. The temperature.

The pressurizing conditions include not only the linear pressure of the processing rolls but also the clearance between the processing rolls, but in the second calendering processing step, the thickness of the melt-blown non-woven fabric thin film laminate to be formed is adjusted. It is preferable that the processing rolls are in a pinched state. The linear pressure of the processing roll is 15 to 130 N / mm, preferably 20 to 100 N / mm, and more preferably 30 to 70 N / mm.

Further, as the processing speed condition, the same conditions as the processing speed condition in the first processing process can be adopted. Specifically, it is 1 to 50 m / min, preferably 2 to 30 m / min, and more preferably 3 to 20 m / min.

In the second calendering processing step according to the present invention, each processing roll that combines a pair of processing rolls is usually heated, but for a combination of a metal roll and an elastic roll, heating is a metal roll. Provided is a combination processing process of an elastic roll at room temperature and a heated metal roll. In addition to heating the metal roll, heating of the elastic roll can also be performed as needed. When both the metal roll and the elastic roll are heated, the metal roll is 40 to 130 ° C., preferably 60 to 120 ° C., more preferably 80 to 110 ° C., and the elastic roll is 40 to 200 ° C., preferably 50 to 50 ° C. Temperature conditions of 150 ° C., more preferably 80 to 120 ° C. can be appropriately adopted.
By a special calendering process using such an elastic roll, the thickness of the melt-blown non-woven fabric thin film laminate can be adjusted, and the effects of thickness uniformity and surface smoothness can be obtained.
The melt-blown non-woven fabric thin film laminate obtained through the first calendering process and the second calendering process can maintain a high degree of openness and can be ultra-thin, and can be ultra-thin under high temperature conditions. The heat shrinkage can be improved, the calender air permeability becomes low resistance, and the tensile strength is also excellent.

The calendering process as a method for producing the melt-blown non-woven fabric thin film laminate according to the present invention is as described above by setting the first calendering process step as the first stage and the second calendering process step as the second stage as described above. If the second calendering process is the first stage and the first calendering process is the second stage, the thickness of the non-woven thin film laminate will be set at the first processing stage, and the latter stage will be effective. In the processing with a gap between the metal rolls, the object to be processed is too thin and the contact with the processing roll becomes loose, and crystallization due to high temperature heat cannot be sufficiently promoted, and residual strain is generated. Since the relaxation is also performed in the subsequent stage, there is a problem that the non-woven thin film laminate, which is a processed product, relaxes and shrinks in the width direction, and there is a problem that it cannot be used as a product due to a shape problem. It is not possible to obtain a quality melt blown non-woven thin film laminate.

C. Third Invention According to the third invention, there is provided a separator for an electric double layer capacitor manufactured by a method including at least a first processing step and a second processing step according to the second invention. Will be done.
In the product-by-process invention, the first processing step alleviates the residual strain generated during the production of the melt-blow non-woven fabric raw fabric, and at the same time, forms a melt-blow non-woven thin film laminate in which the raw material resin component is crystallized. The relaxation of such residual strains and the measurement and quantification of crystallization are technically completely impossible, and even if possible, it is laborious and time consuming to carry them out. It should be protected as a product-by-process invention because it is impractical.
The melt-blown non-woven thin film laminate constituting the separator for an electric double layer capacitor according to the present invention has the above-mentioned characteristics, but proof data have been obtained regarding the specific relationship with the relaxation of residual strain and crystallization. There is a situation that there is no such thing.
From this point of view, it is pointed out that the third invention, the product-by-process invention, should be accepted.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples and the like.
The physical characteristic values of the melt-blown non-woven fabric raw fabric and the melt-blown non-woven fabric thin film laminate described in Examples and Comparative Examples were measured and obtained by the following methods, respectively.
1. Various physical property value measurement methods

(1) Metsuke: A test piece of 100 mm × 100 mm was collected from the length direction of the sample, the weight in the water equilibrium state was measured, and the weight was converted into the basis weight per 1 m2.

(2) Thickness: A test piece of 100 mm × 100 mm was collected from the length direction of the sample and measured with a dial thickness gauge.

(3) Air permeability: A test piece of 100 mm x 100 mm is collected from the sample length direction, and conforms to the "breathability A method (Frazil type method)" of JIS L1096 "General textile test method", and is a Frazier type tester. Was measured using.

(4) Garley air permeability: Measured in accordance with JIS P8117 (2009) +. A Garley Denso meter (manufactured by Toyo Seiki Co., Ltd.) is used as a measuring device, and the sample piece is tightened into a circular hole having a diameter of 10 mm and an area of 78.5 mm2. With an inner cylinder mass of 567 g, air inside the cylinder is passed from the test cylinder portion to the outside of the cylinder. The time through which 300 cc of air passed was measured and used as the Garley value.

(5) Tensile strength and tensile elongation: Measured at a sample width of 25 mm, a grip interval of 100 mm, and a tensile speed of 300 mm / min in accordance with "Tensile strength and elongation" of JIS L1085 "Nonwoven fabric test method".

(6) Average fiber diameter: Take 5 pictures with an electron microscope at any 5 points of the test piece, measure the diameter of 20 fibers per picture, and take a total of these 5 pictures. The diameter of 100 fibers was averaged.

(7) Heat shrinkage rate: Draw 100 mm lines in the MD direction (length direction) and CD direction (width direction) at the center and edges of a 200 mm square sample, and use an oven set at 120 ° C and 150 ° C, respectively. After heating for an hour, the wire length was measured and the dimensional change rate was determined.

(8) Electrolyte liquid absorbency: In accordance with JIS L1907 "Water absorption test method for textile products", one drop of PC (propylene carbonate) was removed from a height of 10 mm on the test piece, and the droplet became the test piece. The time from arrival to the complete disappearance of specular reflection of the droplet was measured with a stopwatch, and the measured value was taken as the absorption rate of the electrolytic solution.

(9) Electrolyte liquid retention property: A test piece of 100 mm × 100 mm is collected and immersed in PC (propylene carbonate) for 60 minutes, then the test piece is taken out and left to hang for 10 minutes. The test piece that retained the liquid was weighed with a balance, and the liquid retention rate was calculated by the following formula.
Liquid retention rate calculation formula: (B)-(A) / (A) x 100 = Liquid retention rate (%)
(However, in the formula, (A): sample weight (B): sample weight after immersion)

(10) Appearance:
The presence or absence of film formation was determined based on the presence or absence of transparent spots having a diameter of 0.5 mm or more in 100 cm2 of the sample piece.
(11) Method for measuring maximum pore diameter, minimum pore diameter, and average pore diameter The average pore diameter and the maximum pore diameter were measured by the bubble point method (ASTM F316-86, JIS K3832) shown below. First, a dry melt-blown non-woven fabric test piece having a diameter of 25 mm was set in an automatic pore size distribution measuring device (model "CFP-1200AX", manufactured by Porous Materials Co., Ltd.), and the air pressure applied to one surface was gradually increased. The pressure P1 when the air started to permeate the drying test piece was obtained, and the dry flow rate curve shown in FIG. 3 was created, and then a half-dry flow rate curve in which the permeation flow rate was halved was created. Similarly, the air pressure applied to one surface of a 25 mm diameter melt-blown non-woven fabric test piece whose pores are filled with a solvent having a surface tension of 16 dyne / cm (trade name "POREWICK", manufactured by Porous Materials) is gradually increased. The pressure P2 when the air started to permeate the wet test piece was obtained, and the wet flow curve shown in FIG. 6 was created.
The average pore diameter Dav was obtained from the pressure Pcross at the intersection of the half-dry flow rate curve and the wet flow rate curve by the following formula.
Dav = 4γcosα / (Pcross-P1)
[However, γ is the surface tension of the solvent, and α is the contact angle of the solvent with respect to polybutylene terephthalate. ]
The maximum pore diameter Dmax was calculated by the following formula.
Dmax = 4γcosα / (P2-P1)
The minimum pore diameter Dmin was obtained by substituting the pressure value when the wet flow rate curve and the dry flow rate curve coincided with P2, which is the equation expressing the above Dmax.
(12) Method for Creating a Pore Diameter Distribution Graph In order to investigate the distribution of the pore diameter, the data obtained by measuring the pore diameter was divided into sections of 0.5 μm units, and the frequencies of each section were totaled to create a histogram. ..
(13) The measurement is performed by applying Statilon DZ4 manufactured by Sisid Electrostatic Co., Ltd. to the electrostatic test piece at a right angle of 30 mm, focusing the red LED, and confirming the polarity value when the LED is in focus.

2. 2. Raw Material Resin for Manufacturing Melt Blow Nonwoven Fabric The following materials were used as the raw material resin for manufacturing melt blow nonwoven fabric.
-Polybutylene terephthalate (PBT); melting point 225 ° C (manufactured by Polyplastics)
-Polypropylene (PP); melting point 165 ° C (manufactured by Japan Polypropylene Corporation)
-Polymethylpentene (PMP); melting point 232 ° C (manufactured by Mitsui Chemicals, Inc.)

Example 1
By the melt blow method described in paragraph [0042] of the present specification, the polybutylene terephthalate (hereinafter, may be referred to as "PBT") is used as a raw material resin, and the PBT melt blow non-woven fabric raw fabrics (A) and (B) are used. Each was manufactured. Specifically, the raw material resin is melted at an extruder temperature of 290 ° C., fed to a die set at 300 ° C., discharged from a die nozzle, and at the same time stretched by a high temperature air blow gas at 310 ° C. to form fine fibers from the nozzle. Collected by a collector installed at a remote location. The nozzle diameter, discharge amount, etc. were appropriately selected so as to obtain a desired non-woven fabric raw fabric together with the melting temperature and die temperature.
Two types of PBT melt-blow non-woven fabric raw fabric (A) having the following fibers having an average fiber diameter of 1.8 μm and PBT melt-blow non-woven fabric raw fabric (B) having fibers having an average fiber diameter of 1.8 μm produced by the above-mentioned production method. Melt blow non-woven fabric raw fabric was prepared.

PBT Melt Blow Nonwoven Fabric Original Fabric (A)
Metsuke (g / m2): 8
Thickness (μm): 86
Air permeability (cc / cm2 / s): 113.4
Tensile strength (N / 25mm width): 4.7
Tensile elongation (%): 32.8
Average fiber diameter (μm): 1.8

PBT Melt Blow Nonwoven Fabric Original Fabric (B)
Metsuke (g / m2): 12
Thickness (μm): 103
Air permeability (cc / cm2 / s): 70.6
Tensile strength (N / 25mm width): 5.5
Tensile elongation (%): 37.3
Average fiber diameter (μm): 1.8

The melt-blown non-woven fabric raw fabric (A) and the melt-blown non-woven fabric raw fabric (B) were superposed and sandwiched between two metal rolls / metal rolls heated to 150 ° C., respectively, under the pressure conditions. The roll pressure was used as the linear pressure of the roll and was subjected to the first calendar processing under the pressure condition of 130 N / mm. A clearance was provided between the metal rolls so that the thickness of the calendering intermediate after the first calendaring was adjusted to a level of about 50 to 70 μm. Steel was used as the material of the metal roll.

A calender having two layers of adhesive layers obtained by heat-sealing some of the fibers existing at the interface between the non-woven fabric raw fabric (A) and the non-woven fabric raw fabric (B) by the first calendering treatment. The processing intermediate was sandwiched between an elastic roll and a metal roll heated to 100 ° C., and further subjected to a second non-woven fabric processing under a pressure condition of 30 N / mm with the roll pressure as the linear pressure of the roll. A melt-blown non-woven fabric thin film laminate composed of two types of non-woven fabric raw fabric (A) and non-woven fabric raw fabric (B) thin films was obtained.
As the elastic roll, one made of a polyamide-based synthetic resin having a shore D hardness of 80 was used. The physical characteristics of the obtained PBT melt blown non-woven fabric thin film laminate (two-layer product (1)) are as follows.

PBT / PBT Melt Blow Nonwoven Fabric Thin Film Two-Layer Laminate (Two-Layer Product 1)
Metsuke (g / m2): 20
Thickness (μm): 33
Garley air permeability (s / φ10 / 300cc): 13.6
Air permeability T (cc / cm2 / s): 5.10
Tensile strength (N / 25mm width): 13.8
Tensile elongation (%): 22.5
Average fiber diameter (μm): 2.6
Appearance (film formation by formation of transparent spots): None Electrolyte absorption rate (seconds): 9.72
Electrolyte retention rate (%): 365
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 1.2
CD: 0.5
Pore diameter distribution (1) Maximum pore diameter (μm) 12.27
(2) Minimum pore diameter (μm) 2.285
(3) Average pore diameter (μm) 6.673
(4) Maximum pore diameter / average pore diameter 1.84
(5) Maximum pore diameter / minimum pore diameter 5.37
(6) Percentage of pores occupying a pore diameter range of 3 to 7 μm (%): 70

As shown in the above results, by laminating and laminating two layers of non-woven fabric having the same average fiber diameter of the constituent fibers, the garley air permeability is 13.6 s / φ10 / 300 cc even though it is a thin film with a thickness of 33 μm. It was possible to maintain a high degree of openness, suppress fiber crushing, and suppress the formation of transparent plaques on the film. Also, the heat shrinkage under high temperature conditions is 0.5% in both the MD and CD directions after heating in an oven set at 120 ° C for 1 hour, and after heating in an oven set at 150 ° C for 1 hour. The dimensional change rate was 1.2% in the MD direction and 0.5% in the CD direction, and good results were obtained. In addition, the electrolyte liquid absorption rate was 9 seconds 72, and the electrolyte liquid retention rate was 365%, which was a remarkable effect, showing an extremely high advantage as a separator for electric double layer capacitors.
It was shown that the pore size distribution of the non-woven fabric laminate that realized such characteristics was remarkably controlled as shown in the graph of FIG.

Example 2
Melt-blow non-woven fabric raw material (C) having the following fibers having an average fiber diameter of 1.8 μm produced by the melt-blow method using the PBT as a raw material resin:

PBT Melt Blow Nonwoven Fabric Original Fabric (C)
Metsuke (g / m2): 7
Thickness (μm): 84
Air permeability (cc / cm2 / s): 121.5
Tensile strength (N / 25mm width): 4.3
Tensile elongation (%): 41.8
Average fiber diameter (μm): 1.8

3 sheets are stacked and sandwiched between two metal rolls / metal rolls heated to 150 ° C., and among the pressure conditions, the roll pressure is the linear pressure of the processing roll and the pressure condition is 130 N / mm. Was used for the first calendar processing. A clearance adjusted so that the thickness of the calendering intermediate had a level of about 50 to 70 μm was provided between the two metal rolls. Steel was used as the material of the metal roll.

The calendering treatment intermediate composed of the three layers of adhesive layers obtained by the first calendering treatment is sandwiched between an elastic roll and a metal roll heated to 100 ° C., and the roll pressure is applied to the processing roll. Under the pressure condition of 30 N / mm as the linear pressure of, the product was further subjected to the second calendar processing treatment to obtain a melt-blown non-woven fabric thin film laminate composed of three layers of non-woven fabric. As the elastic roll, one made of a polyamide-based synthetic resin having the above-mentioned hardness (shore D hardness 80) was used. The physical characteristics of the obtained PBT melt blown non-woven fabric thin film three-layer laminate (three-layer product (1)) are as follows.

PBT / PBT / PBT Melt blow non-woven fabric thin film three-layer laminate (three-layer product 1)
Metsuke (g / m2): 21
Thickness (μm): 31
Garley air permeability (s / φ10 / 300cc): 26.1
Air permeability T (cc / cm2 / s): 2.78
Tensile strength (N / 25mm width): 11.1
Tensile elongation (%): 42.5
Average fiber diameter (μm): 2.9
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 9.97
Electrolyte retention rate (%): 380
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 1.2
CD: 0.5
Pore diameter distribution (1) Maximum pore diameter (μm) 10.75
(2) Minimum pore diameter (μm) 1.865
(3) Average pore diameter (μm) 6.145
(4) Maximum pore diameter / average pore diameter 1.75
(5) Maximum pore diameter / minimum pore diameter 5.76
(6) Percentage of pores occupying a pore diameter range of 3 to 7 μm (%): 85

As shown in the above results, the non-woven thin film laminate composed of three layers having the same average fiber diameter of the constituent fibers has a thickness of 31 μm, a garley air permeability of 26.1 s / φ10 / 300 cc, and a high opening. It was possible to maintain the degree, suppress the crushing of fibers, and suppress the formation of transparent spots on the film. In addition, the heat shrinkage under high temperature conditions is 0.5% for both MD and CD after heating in an oven set at 120 ° C for 1 hour, and even after heating in an oven set at 150 ° C for 1 hour. The dimensional change rate was 1.2% in the MD direction and 0.5% in the CD direction, and good results were obtained. Further, the electrolyte liquid absorption rate was 9 seconds 97, and the electrolyte liquid retention rate was 380%, which was a remarkable effect, showing an extremely high superiority as a separator for an electric double layer capacitor.
The non-woven thin film laminates that have realized such characteristics have pore size distributions (1) to (6), and as shown in the graph of FIG. 2, the pore size distribution is remarkably controlled as described above. It has been shown.

Example 3
The PBT melt-blow non-woven fabric raw fabric (C) having fibers having an average fiber diameter of 1.8 μm and the PMP melt-blow non-woven fabric raw fabric (D) having the following fibers having an average fiber diameter of 2.9 μm used in Example 2:
PMP Melt Blow Nonwoven Fabric Original Fabric (D):
Metsuke (g / m2): 8
Thickness (μm): 208
Air permeability (cc / cm2 / s): 273
Tensile strength (N / 25mm width): 2.7
Tensile elongation (%): 29.8
Average fiber diameter (μm): 2.9

Under the same conditions and operations as in Example 2 by stacking the PBT melt-blow non-woven fabric raw fabric (C) / PMP melt-blow non-woven fabric raw fabric (D) / PBT melt-blow non-woven fabric raw fabric (C) so as to form three layers. , The first calender processing treatment and the second calender processing treatment were carried out to obtain the PBT melt blow non-woven fabric thin film / PMP melt blow non-woven fabric thin film / PBT melt blow non-woven fabric thin film three-layer laminate (three-layer product 2) shown below.

PBT melt blow non-woven fabric thin film / PMP melt blow non-woven fabric thin film / PBT melt blow non-woven fabric thin film three-layer laminate (three-layer product 2)
Metsuke (g): 22
Thickness (μm): 40
Garley air permeability (s / φ10 / 300cc): 22.1
Air permeability T (cc / cm2 / s): 3.17
Tensile strength (N / 25mm width): 12.7
Tensile elongation (%): 27.6
Average fiber diameter: 2.4
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 18.72
Electrolyte retention rate (%): 280
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 0
CD: 0
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 0.5
CD: 0.5
Pore diameter distribution (1) Maximum pore diameter: 14.58
(2) Minimum pore diameter: 2.885
(3) Average pore diameter: 7.964
(4) Maximum pore diameter / average pore diameter: 1.83
(5) Maximum pore diameter / minimum pore diameter: 5.05

As described above, by adopting the three-layer structure of PBT / PMP / PBT, the maximum is the same as the two-layer structure of PBT / PBT of Example 1 and the three-layer structure of PBT / PBT / PBT of Example 2. It shows a unique pore diameter distribution with a pore diameter / average pore diameter of less than 2.00 and a maximum pore diameter / minimum pore diameter of 5.00 or more, and also has high Garley air permeability in terms of characteristics, especially the heat shrinkage rate. Was small, and excellent high temperature stability was obtained.

Comparative Example 1
PBT melt blown non-woven fabric raw fabric ( E ) having fibers with an average fiber diameter of 1.8 μm shown below:

PBT Melt Blow Nonwoven Fabric Original Fabric (E):
Metsuke (g / m2): 15
Thickness (μm): 154
Air permeability (cc / cm2 / s): 29.6
Tensile strength (N / 25mm width): 8.1
Tensile elongation (%): 14.7
Average fiber diameter (μm): 1.8

Was subjected to the first calender processing treatment and the second calender processing treatment under the same conditions and operations as in Example 1 to obtain a PBT melt blown non-woven fabric thin film single layer (single layer comparative product (a)). The physical properties of the obtained PBT melt-blown non-woven fabric thin film single-layer body (single-layer comparative product (a)) are as follows, and the electrolyte liquid retention rate and the heat shrinkage rate deviate from the scope of the present invention.

PBT Melt Blow Nonwoven Fabric Thin Film Single Layer a (Single Layer Comparative Product (a))
Metsuke (g / m2): 15
Thickness (μm): 28
Garley air permeability (s / φ10 / 300cc): 8.7
Air permeability T (cc / cm2 / s): 5.24
Tensile strength (N / 25mm width): 10.2
Tensile elongation (%): 22.6
Average fiber diameter (μm): 2.3
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 8.95
Electrolyte retention rate (%): 250
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 1.0
CD: 0.5
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 1.5
CD: 1.0
The pore size distribution of the melt-blown non-woven fabric thin film single-layer body a (single-layer comparative product (a)) is as shown in the following (1) to (6).
Pore diameter distribution (1) Maximum pore diameter (μm) 18.14
(2) Minimum pore diameter (μm) 4.552
(3) Average pore diameter (μm) 8.766
(4) Maximum pore diameter / average pore diameter 2.07
(5) Maximum pore diameter / minimum pore diameter 3.99
(6) Percentage of pores occupying a pore diameter range of 3 to 7 μm (%): 33

As shown in the pore diameter distribution, (1) maximum pore diameter, (2) minimum pore diameter, (3) average pore diameter, (4) maximum pore diameter / average pore diameter and (5) maximum pore diameter / minimum fineness. All of the pore diameters were outside the scope of the present invention, and sufficient effects were not obtained on high temperature stability and electrolyte liquid retention.

Comparative Example 2
The melt-blown non-woven fabric raw fabrics (A) and (B) used in Example 1 were not subjected to the first calendering treatment, but were subjected only to the second calendering treatment. The conditions and operations of the second calendering process were the same as those of the second calendering process of Example 1.
By the calendering treatment, a PBT melt-blown non-woven fabric thin film two-layer laminate b (two-layer comparative product (b)) having the following physical properties was obtained.

PBT Melt Blow Nonwoven Fabric Thin Film Two-Layer Laminated Body b (Two-Layer Comparative Product (b))
Metsuke (g / m2): 20
Thickness (μm): 45
Garley air permeability (cc / cm2 / s): 3.5
Air permeability (cc / cm2 / s): 13.47
Tensile strength (N / 25mm width): 9.3
Tensile elongation (%): 38.8
Average fiber diameter (μm): 3.0
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 9.39
Electrolyte retention rate (%): 390
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 2.0
CD: 1.5
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 4.5
CD: 3.0
Pore diameter distribution (1) Maximum pore diameter (μm) 19.35
(2) Minimum pore diameter (μm) 5.217
(3) Average pore diameter (μm) 13.38
(4) Maximum pore diameter / average pore diameter 1.45
(5) Maximum pore diameter / minimum pore diameter 3.71

As described above, the PBT melt-blow non-woven fabric two-layer laminate b (two-layer comparative product (b)) obtained in Comparative Example 2 is the PBT melt-blow non-woven fabric thin film two-layer laminate of Example 1, but is subjected to the first calendar processing treatment. As a result of omitting the above, the pore size distributions (1) to (3) and (5) deviate from the scope of the present invention, have a high heat shrinkage rate, and lack high temperature stability.

Comparative Example 3
PBT melt blown non-woven fabric raw fabric (F) having the following physical properties:

PBT Melt Blow Nonwoven Fabric Original Fabric (F)
Metsuke (g / m2): 20
Thickness (μm): 175
Air permeability (cc / cm2 / s): 38.7
Tensile strength (N / 25mm width): 9.6
Tensile elongation (%): 15.8
Average fiber diameter (μm): 1.8

Was subjected only to the second calendar processing without being subjected to the first calendar processing under the same conditions and operations as those of Comparative Example 2 except that the temperature of the second processing was set to 180 ° C. ..
The obtained PBT melt blown non-woven fabric thin film single layer c (single layer comparative product (c)) has the following physical properties.

PBT Melt Blow Nonwoven Fabric Thin Film Single Layer c (Single Layer Comparative Product (c))
Metsuke (g / m2): 20
Thickness (μm): 30
Garley air permeability (cc / φ10 / 300cc): 210
Air permeability T (cc / cm2 / s): 1.17
Tensile strength (N / 25mm width): 14.8
Tensile elongation (%): 19.4
Average fiber diameter (μm): 3.0
Appearance (film formation by forming transparent spots): Yes Electrolyte absorption rate (seconds): 11.2
Electrolyte retention rate (%): 245
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 0
CD: 0
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 1.0
CD: 0.5
Pore diameter distribution (1) Maximum pore diameter (μm) 12.13
(2) Minimum pore diameter (μm) 2.84
(3) Average pore diameter (μm) 6.007
(4) Maximum pore diameter / average pore diameter 2.02
(5) Maximum pore diameter / minimum pore diameter 4.27

As described above, the first calendering process is omitted and only the second calendering process is performed. Moreover, in the high temperature processing process, film formation due to transparent spots occurs and the air permeability is lowered, so that the film can be used as a separator. No non-woven fabric thin film having such characteristics was obtained.

Comparative Example 4
Same as Comparative Example 1 except that the same PBT melt blown non-woven fabric raw fabric (F) used in Comparative Example 3 was subjected to only the first calendering treatment without being subjected to the second calendering treatment. When subjected to the calendering treatment under the conditions and operations of the above, a PBT melt-blown non-woven fabric thin film monolayer d (single-layer comparative product (d)) having the following physical properties was obtained.

PBT Melt Blow Nonwoven Fabric Thin Film Single Layer d (Single Layer Comparative Product (d))
Metsuke (g / m2): 20
Thickness (μm): 42
Garley air permeability (s / φ10 / 300cc): 87
Air permeability (cc / cm2 / s): 4.42
Tensile strength (N / 25mm width): 20.5
Tensile elongation (%): 12.9
Average fiber diameter (μm): 3.6
Appearance (film formation by forming transparent spots): Yes Electrolyte absorption rate (seconds): 14.18
Electrolyte retention rate (%): 155
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 1.5
CD: 1.0
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 2.5
CD: 1.5
Pore diameter distribution (1) Maximum pore diameter (μm): 14.65
(2) Minimum pore diameter (μm): 5.355
(3) Average pore diameter (μm): 9.982
(4) Maximum pore diameter / average pore diameter: 1.47
(5) Maximum pore diameter / minimum pore diameter: 2.74
(6) Percentage of pores occupying a pore diameter range of 3 to 7 μm (%): 1

As described above, only by the first calendering treatment, film formation occurred due to the formation of transparent spots, and the necessary characteristics as a separator such as a decrease in air permeability and an increase in heat shrinkage were not obtained.

Comparative Example 5
The following PP melt blown non-woven fabric raw material (G) produced by the melt blow method using the polypropylene as a raw material resin:

PP Melt Blow Nonwoven Fabric Original Fabric (G)
Metsuke (g / m2): 7
Thickness (μm): 111
Air permeability (cc / cm2 / s): 103
Tensile strength (N / 25mm width): 2.7
Tensile elongation (%): 42.7
Average fiber diameter (μm): 3.2

PP melt blown non-woven fabric thin film having the following physical properties by adopting the same calendar processing conditions and operations as those of Comparative Example 2 except that the above was used only for the second calendar processing at a processing temperature of 65 ° C. A layer e (single-layer comparative product (e)) was obtained.

PP melt blown non-woven thin film single layer e (single layer comparative product (e))
Metsuke (g / m2): 7
Thickness (μm): 20
Garley air permeability (s / φ10 / 300cc): 8.8
Air permeability (cc / cm2 / s): 6.7
Tensile strength (N / 25mm width): 3.8
Tensile elongation (%): 23.5
Average fiber diameter (μm): 3.6
Appearance (film formation by forming transparent spots): None Electrolyte absorption rate (seconds): 30 or more Electrolyte retention rate (%): 65
Heat shrinkage rate (%):
(In an oven at 120 ° C
Dimensional change rate after heating for 1 hour) MD: 5.5
CD: 5.0
(In an oven at 150 ° C
Dimensional change rate after heating for 1 hour) MD: 12.5
CD: 10.0
Pore distribution (1) Maximum pore diameter (μm): 13.33
(2) Minimum pore diameter (μm): 1.566
(3) Average pore diameter (μm): 4.568
(4) Maximum pore diameter / average pore diameter: 2.92
(5) Maximum pore diameter / minimum pore diameter: 8.51
(6) Percentage of pores occupying a pore diameter range of 3 to 7 μm (%): 70

As described above, the melt-blown non-woven fabric thin film monolayer made of polypropylene obtained only by the second calendering process does not satisfy all the requirements (1) to (6) in the pore distribution, and has a heat shrinkage rate. However, the electrolyte holding property was also low, and the properties required for a separator were lacking.

The contents of the above examples and comparative examples are summarized in Table 1.
From the results of Examples and Comparative Examples, the melt-blow non-woven fabric thin film laminate having two or more layers of the melt-blow non-woven fabric thin film produced using a heat-resistant resin as a raw material resin has a peculiar pore size distribution as described above, and holds the electrolytic solution. It has excellent liquid properties and high-temperature stability, was realized by the first calendering process and the second calendering process, and was found to have extremely high performance as a separator for electric double layer capacitors.

Claims (14)

A separator for an electric double layer capacitor composed of a melt-blow non-woven fabric thin film laminate in which at least two layers of melt-blow non-woven fabric thin films are laminated.
The average fiber diameter of the fibers constituting the melt-blown non-woven thin film laminate is 0.5 to 15 μm, the Garley air permeability is 1 to 40 s / φ10 / 300 cc, and the heat shrinkage is 150 ° C. for 1 hour. After the heat treatment under the conditions, the shrinkage change of either the shape in the MD direction or the CD direction is expressed by the dimensional change rate, which is 1.2% or less, and the electrolyte liquid retention rate is 260% or more. Separator for electric double layer capacitors.
The separator for an electric double layer capacitor according to claim 1, wherein the average fiber diameters of the constituent fibers of each layer of at least two layers of the melt-blown non-woven fabric thin film constituting the melt-blown non-woven fabric thin film laminate are substantially the same or different from each other.
The first aspect of claim 1, wherein the melt-blown non-woven fabric thin film laminate is an interlayer adhesion processed body formed by partial heat fusion of fibers existing at the interface between layers of at least two layers of the melt-blow non-woven fabric thin film constituting the same. Separator for electric double layer capacitors.
The separator for an electric double layer capacitor according to claim 1, wherein the proportion of pores occupying a pore diameter in the range of 3 to 7 μm is 50% or more among all the pores of the melt-blown non-woven fabric thin film laminate.
The separator for an electric double layer capacitor according to claim 1, wherein the melt-blown non-woven fabric thin film laminate has a pore size distribution satisfying the following (1) to (5).
(1) Maximum pore diameter: 15 μm or less (2) Minimum pore diameter: 3 μm or less (3) Average pore diameter: 8 μm or less (4) Maximum pore diameter / average pore diameter: less than 2.00 (5) Maximum pore diameter / minimum Pore diameter: 5.00 or more
The separator for an electric double layer capacitor according to claim 1, wherein the constituent material of the melt-blown non-woven fabric thin film laminate is a heat-resistant resin.
A method for manufacturing a separator for an electric double layer capacitor composed of at least two layers of melt-blown non-woven thin film laminates.
(A) At least two melt-blown non-woven fabric raw materials are superposed, and the calendar mechanism having a metal roll suppresses the processing temperature conditions above the glass transition point of the raw material resin and the crushing of the constituent fibers of the melt-blown non-woven fabric raw material. In addition, the first calendar processing step to be performed in the calendar processing under the pressure condition adjusted to the condition that the film can be thinned, and
(B) The calendar processing intermediate obtained by the first calendar processing step has an effective processing temperature condition and the crushing of the constituent fibers of the non-woven fabric is suppressed by the calendar mechanism having at least one elastic roll. The melt blow is characterized by having a calendar processing step including at least a second calendar processing step to be subjected to calendar processing under pressurized conditions adjusted to a condition capable of thinning. A method for manufacturing a separator for an electric double-layer capacitor composed of a non-woven thin film laminate.
The method for manufacturing an electric double layer capacitor separator according to claim 6, wherein in the first calender processing step, the processing temperature condition above the glass transition point is 130 ° C. or higher.
According to claim 7, the linear pressure of the metal roll is 200 N / mm or less among the pressure conditions adjusted so as to suppress the crushing of the constituent fibers of the melt-blown nonwoven fabric in the first calendering process. The method for manufacturing a separator for an electric double layer capacitor described. The seventh aspect of claim 7, wherein in the second calendar processing step, the calendar mechanism includes a combination of at least a pair of processing rolls, and the combination of the pair of processing rolls includes a combination of an elastic roll and a metal roll. Manufacturing method of separator for electric double layer capacitor.
The seventh aspect of claim 7, wherein in the second calendar processing step, the calendar mechanism includes a combination of at least a pair of processing rolls, and the combination of the pair of processing rolls includes a combination of elastic rolls and elastic rolls. Manufacturing method of separator for electric double layer capacitor.
The method for manufacturing an electric double layer capacitor separator according to claim 7, wherein the effective processing temperature condition is a temperature of 130 ° C. or lower in the second calender processing step.
The method for manufacturing an electric double layer capacitor separator according to claim 7 or 12, wherein in the second calendering process, the elastic material of the elastic roll is a synthetic resin.
Next step:
(A) At least two melt-blown non-woven fabric raw materials are superposed, and the metal roll suppresses the processing temperature conditions above the glass transition point of the raw material resin and the crushing of the constituent fibers of the melt-blown non-woven fabric raw material, and makes the material thinner. The first calendering process, which is subjected to calendering under pressurized conditions adjusted to the possible conditions,
(B) The calendar processing intermediate obtained in the first calendar processing step has an elastic roll, so that effective processing temperature conditions and crushing of constituent fibers of the nonwoven fabric are suppressed, and A separator for an electric double-layer capacitor manufactured by a method including a second calendering process step of being subjected to calendering under pressurized conditions adjusted to a thinning possible condition.